Listening to Elephants

8/3/2019 Listening to Elephants

1/34


2/34

Acoustic is a sound signals which theytravel in all directions.

Acoustic signals are useful for givinginformation about an immediatesituation.

Elephants are specialists in theproduction of low frequency soundand in the use of long-distancecommunication.


3/34

Because low-frequency soundattenuates very little with

distance, elephants powerfulinfrasonic calls enable themto stay in contact as they

move separately over largeareas of savannah or forest.


4/34

Types of Freqeuncy Example of calls

High Frequency Trumpets

Snorts

Barks

RoarsCries

Low Frequency Chirps

Rumbles


5/34

A typical human male's voice inspeech fluctuates around 110 Hertz(Hz, or cycles per second), afemale's voice around 220 Hz and achild's around 300 Hz.

Among elephants, a typical malerumble fluctuates around an averageminimum of 12 Hz (more than 3octaves below a man's voice), afemale's rumble around 13 Hz and acalf's around 22 Hz.


6/34

a single elephant call may startwith a rumble at 27 Hz andgrading into a roar at 470 Hz!

Elephants can produce verygentle, soft sounds as well asextremely powerful sounds.


7/34

Sound is produced as air expelled from the lungs ispassed over the vocal chords or larynx(7.5cm).

The moving air causes the vocal chords to vibrateat a particular frequency depending upon the type

of sound the elephant is making.

By lengthening or shortening the vocal chords anelephant can produce a wide range of frequencies.


8/34

The column of air vibrates in the elephant'sextended vocal tract or resonating chamber isdepending on how the elephant holds the

components of this chamber (trunk, mouth,tongue, pharyngeal pouch, larynx).

Thus, it is able to modify and amplifydifferent components of the sound.


9/34

If hold elephants head in a certainposture and by flapping its ears in a

particular rhythm and angle, thiscan affect the musculature aroundthe larynx, thus modifying a

particular call to achieve the desiredsound.


10/34

Has a large body just as in musical instruments,the longer and looser the vibrating string (or vocalchords) and the larger the resonating chamber, the

lower the frequency produced.

The structures of the hyoid apparatus and the

musculature that support the tongue and the larynxhad created a loose arrangement allows for agreater movement and flexibility of the larynxwhich facilitate the production and resonance of lowfrequency sound.


11/34

The larger the space between an animal'sears (the inter-aural distance) the betterthe ability at localizing sound because thedifference in the time and intensity of asound reaching each ear can be used as cuesin localizing sound.

Elephants extend their ears perpendicularlyto their heads in order to better localizesounds.


12/34


13/34

(1) Elephant Listening Project began atthe Portland Zoo in 1984.

(2) Focus of the research:

Characterizing low frequency communication insavannah elephants.

Characterizing low frequency communication inforest elephants in rainforest of central Afirca

Conservation of forest elephants in Central Africa.


14/34


15/34

Infants and calves < 5 years may emit a cry orcry-rumble when they are in some form of distresssuch as when denied access to the breast or when

protesting unwanted contact by an older elephant.

Cries are very short whimpering sounds lasting lessthan half a second in duration. Cries are typicallyfollowed by a rumble without an inhalation, andrarely a cry may be both preceded and followed bya rumble.


16/34

Produced by several different individuals and associatedwith the sucking of water or odors into the mouth. In Amboseli, only 2 in a population of 1500 elephants emitthis unusual sound.

Example: Gail and Gwen, are adult females from the samefamily. For many years only Gail was heard to croak, butthen Gwen began croaking. Gwen and Gail are sisters andclose associates. Thus, researcher suggest that the croak isanother example of vocal learning.

Besides, both Amboseli elephants appear to croakwhen they are relaxed and feeding howevercroaking appears to have no communicative

function.


17/34

Spectrograms of elephant vocalizations ( Croaking)579-633HZ


18/34

Bark Barks are transient and primarily noisy calls that

differ from noisy roars in their very shortduration. Similar to the roars, barks may becombined with a rumble producing acomposite bark-rumble.

In Amboseli barks and bark-rumbles were heardvery infrequently, but occurred in contexts similarto roars by calves: in the context of begging and

when elephants were tusked or pushed.

Barks are transient and primarily noisy calls thatdiffer from noisy roars in their very shortduration. Similar to the roars, barks may becombined with a rumble producing acomposite bark-rumble.

In Amboseli barks and bark-rumbles were heardvery infrequently, but occurred in contexts similarto roars by calves: in the context of begging and

when elephants were tusked or pushed.


19/34

Rev

The rev was described in 2003 by Leong andher colleagues as a short tonal harmonicvocalization, less than a second in duration,

and almost always followed immediately by arumble.

The structure of the rev is similar to a shortrumble, but at between 50 and 90 Hz itsfundamental frequency is significantly higherthan any known rumble. The revs recorded incaptivity by Leong are buzzing or revvingsounds.


20/34

Rev from 1-1.5 s then rumble(127-282 hz)


21/34

grunt

The grunt was described in 2007 byStoeger-Horwath:

as a soft, short, beeping or honkingsound produced by infant elephantsin the first days of life.

She reports that in captivity infantscease producing grunts by two months

of age. Grunts are barely audible and,therefore, difficult to hear and recordin the wild. Some are associated withattempts to suckle.


22/34

SNORT

Short, noisy, broadband soundsproduced by blowing air purposefullythrough the trunk.

Why do elephants snort?

Surprised by something

Intense social excitement

To alert other members of their group to

a new situation.


23/34

Audibly distinguishable from themore common "blows" (blowing,sneezing, wheezing and coughingsounds).

Sound sharper and more purposefulthan a blow.


24/34

Spectrogram of Elephant Snorting


25/34

RUMBLES

Most frequently heard call type acrossboth sexes and all ages.

Easily distinguished by their very lowfrequencies and clear harmonicstructure.

Originate in the larynx (source) andresonate (filter) through the pharyngealpouch, the nasal passages of the skulland through the trunk.


26/34

Can be produced with the mouth

open or apparently closed.

Open-mouthed calling is associated

with the louder, more modulated

rumbles.

Highly variable, graded calls

containing fundamental frequencies

ranging between 8 and 34 Hz.


27/34

Depends upon the callers age, size andexcitement level, as well as the call

context-type.

Over 90% of the calls in our databaseare rumbles.

Range in duration from less than half asecond to almost 12 seconds.

The rumbles of older individuals arelonger in duration and lower in frequencythan those of younger individuals.


28/34

Spectrogram of Rumble Greeting


29/34

Trumpet

Produced by a forcefulexpulsion of air through thetrunk and come in severalforms.

4055879 Hz with a meanduration of about 1 s.

Trumpets are mainly tonal

sounds, though harmonics areoverlaid with noise. Mostlast less than a second(though extremely longtrumpets may last over 3seconds).


30/34

Elephants tend to trumpet when they arehighly stimulated - in situations where they

may be fearful, surprised, aggressive,playful or socially excited.

Trumpeting is often associated with

intensely social events such as a birth,mating or greeting ceremony, where groupparticipation is important.

Function as a kind of "exclamation mark",expressing the very high level ofexcitement and importance of the event.


31/34

Squelching

This low-frequency sound is apparently producedby forcing air through a "scrunched-up" trunk.Sometimes the individual squelching gives theimpression of having a genuine itch in his or hertrunk, but at other times production of this ratherodd bubbling sound seems to be an end in itself.

Squelching is most often heard when elephants arerelaxed, for example standing by the side of awaterhole, or waiting patiently for other familymembers to move


32/34

Truck-like

In an article entitled, Elephants are capableof vocal learning, published in the journal,Nature, in 2005, Poole and her colleagues

(researchers) reported the imitations oftruck sounds by a ten-year-old adolescentfemale African elephant, Malaika, who wasliving in a semi-captive group of orphaned

elephants in Tsavo, Kenya.


33/34

With a fundamental frequency hovering around 50Hz (similar to trucks) and highly variable duration

(range: 685 ms to almost 15 seconds) thissound is unlike any call in the normal repertoire ofAfrican elephants.

Poole and her colleagues were able to showstatistically that the elephant was imitating thenoise of distant trucks. Since the publication of the2005 paper additional elephants in the small Tsavogroup of orphans learned to produce the same

sound.


34/34

Documents

Listening to Elephants